There are storage apparatuses that perform hierarchical control to store frequently-accessed data in a high-speed device such as a solid state drive (SSD) and the like, and to store infrequently-accessed data in a low-speed device such as a hard disk drive (HDD) and the like.
Such a storage apparatus often handles data managed by a log-structured file system. In this case, the storage apparatus makes a change to the data by adding instead of overwriting.
See for example, Japanese Laid-open Patent Publications No. 2003-216460, and No. 2014-041645.
In hierarchical control, the storage apparatus appropriately performs data relocation such that frequently-accessed data is placed in a high-speed device with a high access speed.
If an update is made to a file managed by the log-structured file system, the file after the update is stored in a location different from the location where the file before the updated is stored. Thus, after the update of the file, the location where the file after the update is stored is mostly accessed.
Accordingly, in the case where an update is made to a file managed by the log-structured file system after the file is relocated to a high-speed device, the frequency of access to the file before the update in the high-speed device decreases. This reduces the use efficiency of the high-speed device.